Thanks guys! Turns out kids e bikes are fun to build because of the low power requirement and low top speed. I have that BBS02 set at only 8 amps (48v so less than 400 watts) and the top speed set at 12-14mph. 3 AH 12S Lipo last for an hour or two and are cheap if I decide to get some spares. I wanna build another bike with a 210 rpm Q100H in the rear 20 in wheel. Maybe not a fat bike but a Kona Shredder 20. I think the 210 rpm motor in the 20 in wheel would have good torque and a low top speed, maybe 24 or 36 volt. I'd wanna make it super stealth. Also, the price of this thing really wasn't bad when you compare it to the OSET 12.5 I got him when he was two and a half, that was $800. I've got less in this and it should be good for several years. Can't wait for the snow!

Awesome! I love the look of those 20" fat tire bikes, to me even better than the big ones. The fastest route to an all electric future is to give an ebike to every kid in the world.

If stealth is mandatory then sure go with the geared hubbie. I don't care about stealth, so for kids I direct people toward a beefy DD hubbie in a small wheel driven by a capable programmable controller. That gives absolute reliability and an easy upgrade path as their abilities and experience grow. You're spot on about the advantages vs the ebikes we build for ourselves, since low power, load, and range make it so simple that even real motorcycle performance is easily possible with hubbies, and taking advantage of the small wheel advantages doesn't look out of place.

As you stated, you were re-purposing a kit that you already had. For anyone who is interested in doing something similar...if you are running a lower power level (like this), then you have the option of buying the 36V BBS01, which would allow you to use a wide variety of 36V battery packs, which might be more affordable and easier to fit (physically smaller)...

spinningmagnets wrote:As you stated, you were re-purposing a kit that you already had. For anyone who is interested in doing something similar...if you are running a lower power level (like this), then you have the option of buying the 36V BBS01, which would allow you to use a wide variety of 36V battery packs.

That being said, you are one of the coolest dads ever!

Thanks! I've been thinking of building another bike for him. Now I'm thinking a friction drive would be the easiest, lightest, cheapest, also the most stealth. Should be easy because he weighs only 50 lbs and I limit his top speed to 14 mph in open areas. I'd like to build a 500w friction drive with a 10 mph top speed so he can get up the mild hills at our local MTB trails. This bike is great around the neiborhood but I'd like something lighter and stealthier for MTB trails.